Method of producing metallic beryllium



1940, v B. F. KJELLGREN Er AL 2,188,904

METHOD OF PRODUCING METALLIC BERYLLIUM Filed March 16, 1936 Deg. Cent.

I0 3o 40 so so so no07 'z I00 so 70 60 50 40 -30 20 I0 0 %LiCI+KCI+NaCI Eutectic Patented Feb. 6, 1940 UNITED STATES METHOD OF PRODUCING METALLIC BERYLLIUM Bengt R. F. Kjellgren and Charles B. Sawyer, Cleveland Heights, Ohio, assignors to The Brush Beryllium Company, Cleveland, Ohio, a corpo ration of Ohio Application March 16, 1936, Serial No. 69,096

3 Claims.

. This invention relates to an improved method of producing metallic beryllium from beryllium chloride by electrolysis of the said chloride in a molten bath.

Since beryllium chloride is a non-conductor of electricity it cannot be electrolyzed alone. To overcome this difficulty it was early proposed by W. Borchers (Zeitschriit iiir Electrochemie, vol. 2, 39,. 1895) to electrolyze a ncited mixture of .beryllium chloride with alkaline chlorides or alkaline earth chlorides. Borchers carried out the electrolysis in a wrought iron crucible which'at the same time served as the cathode with a carbon rod for the anode. The molten mixture was heated with gas to a temperature just reaching the melting point of beryllium (1278 C.) As beryllium chloride boils at about 500 C. it is clear that the melt used by Borchers must havecontained a substantially lessened amount of beryllium chloride. Since Borchers work others have electrolyzed melted mixtures of beryllium chloride and sodium chloride at temperatures of about 800 C. -At thistemperature also the losses of beryllium chloride due to volatilization are considerable and in practice it would be necessary to recover the volatilized beryllium chloride in the interest of economy.

An object of the present invention is to provide a method of electrolysis of beryllium chloride in which losses due to volatilization are eliminated or minimized at the temperature at which the electrolysisis carried out.

A further object of the'invention is to minimize the amount of electical energy consumed in the production of metallic beryllium by electrolysis through the use of heat from gas or other low-cost fuels for maintaining the electrolyte in amolten condition.

Another object of the invention is to overcome difliculties with the materials used in the construction'of the electrolyzer, such as characterize methods of electrolysis at high temperatures.

Another object of the invention is the reduction of chemical attack on anodes, cathodes, and a chloride and sodium chloride, which has a freezing point-of 362 C., beryllium chloride may be 'added in varying proportions to produce a corresponding series of such low freezing point mixtures. 5

The freezing point of these mixtures are shown by the graph in the accompanying drawing. In this drawing ordinates represent centigrade melting temperatures and abscissas represent percentage proportions by weight of the beryllium 10 chloride to the remainder of the electrolyte mixture. From the graph it will be noted that a mixture containing 50% BeClz and 50% KCl, LiCl, NaCl eutectic melts as low as 238 C. This mixture contains 20.2% LiCl, 26.6% KCl, 3.2% Ill NaCl and 50% BeClz. The viscosity of this mix ture at 260-270 C. is sufficiently low to permit an eificient electrolysis.

It will be observed further from the graph of the drawing that combinations of the eutectic 20 mixture with BeClz up to 50% 36012 have melting points ranging from about 238 C. to the relatively low temperature of 385 C. and are suitable for electrolysis at temperatures substantially below the boiling point of BeC122.

It is to be observed further, in connection with the graph of the drawing, that the melting point (362) of the eutectic mixtureof KCl LiCl and NaCl is not only, far below the boiling point or beryllium chloride but also substantially below 30 its melting point of about 400 C. Consequently the eutectic mixture can be prepared in the molten state and the beryllium chloride added thereto .with practically no volatilization and loss of the beryllium chloride. 35

Another advantage of our low melting point eutectic mixture combined with beryllium chloride is that close regulation of the amount of beryllium chloride in the bath is not necessary since the electrolylytic bath cannot be solidified 40 even by electrolyzing out all of the beryllium chloride if the bath is maintained above about 385 C.

In carrying out our method of electrolysis it is not necessary to use the eutectic mixture of KCl, LiCl and NaCl. The freezing points of various 5 mixtures of these three salts and of three component mixtures of various other alkali salts and alkaline earth salts have heretofore been determined. In the International Critical Tables, Vol. IV, there are given three-component 5 freezing point diagrams of the KC], LiCl and NaCl mixture and of various other alkaline chloride and alkaline earth chloride mixtures. Thus, from the proper diagram, proportions of 'melts of KC], LiCl and NaCl may be taken and anhydrous I Y I BeClz added to make mixtures with melting points below the boiling point of beryllium chloride. As BeClz even at its melting point has a considerable vapor pressure it is desirable to carry out the electrolysis below 400 C. but temto have suiiiciently low melting points for the purpose of carrying out our method. For example, we may use eutectic mixtures, or mixtures approaching the eutectic compositions, as follows:

Freezing Composition of eutectic point The foregoing eutectic mixtures serve only as examples of mixtures of alkali chlorides or alkaline earth chlorides that may be used with anhydrous beryllium chloride to produce melts having melting points suitable for electrolyzing beryllium chloride below its boiling point. In

this connection it is observed that, in order to celain, pyrex glass, or quartz may conveniently be used. The low temperature at which the electrolysis is carried out makes possible the use of a much wider variety of such materials than would be possible at the higher temperature used in prior processes. The container may be heated externally with a gas flame. The cathode may consist of a. metal sheet. of aluminum, copper, nickel or other suitable material. Graphite may be used for the anode'as we have found that graphite is not noticeably attacked by the chlorine released during electrolysis at the low electrolyte temperatures which we are able to employ. l

By way of illustration and for the purpose of more clearly explaining the invention we give the following description of one suitable procedureiollowed in carrying out our process:

796 grams KCl, 610 grams L101, 93 grams NaCl and 1500 grams BeCla were melted in a quartz container heated externally to about 300 C.

One aluminum sheet cathode and two graphite plate anodes were used, the cathode being. placed between the anodes so that beryllium was deposited on both sides of the cathode. The electrolysis lasted 24 hours, 20 minutes and the temperature varied between 290 C. and 326 C. The voltage required for the decomposition of the beryllium chloride was 2.2 volts and the current 1. The process of producing metallic beryllium which comprises electrolyzing beryllium chloride from a molten bath consisting of beryllium chloride and a eutectic mixture of potassium chloride, lithium chloride and sodium chloride, the beryllium chloride constituting from 40% to 52% by weight of the bath.

2. The process of producing metallic beryllium which comprises forming a mixture made up of approximately 50% by weight of beryllium chloride, 20.2% lithium chloride, 26.6% potassium chloride and 3.2% sodium chloride, and electrolyzing the beryllium chloride from a molten bath of the said mixture while thebath is maintained at a temperature between-260 C. and 300 C.

3. The process of producing metallic beryllium which comprises adding anhydrous beryllium chloride to a mixture of lithium chloride, potassium chloride and sodium chloride combined in substantially eutectic proportions and having a meltingpoint below the melting point of anhydrous beryllium chloride, the beryllium chloride making up from'a'bout to about 90% of all the materials, and electrolyzing the BnNG'r R. F. KJELLGREN. CHARLES B. SAWYER. 

